Effect of local chemistry and structure on thermal transport in doped GaAs

Abstract

Using a first-principles approach, we analyze the impact of DX centers formed by S, Se, and Te dopant atoms on the thermal conductivity of GaAs. Our results are in good agreement with experiments and unveil the physics behind the drastically different effect of each kind of defect. We establish a causal chain linking the electronic structure of the dopants to the thermal conductivity of the bulk solid, a macroscopic transport coefficient. Specifically, the presence of lone pairs leads to the formation of structurally asymmetric DX centers that cause resonant scattering of incident phonons. The effect of such resonances is magnified when they affect the part of the spectrum most relevant for thermal transport. We show that these resonances are associated with localized vibrational modes in the perturbed phonon spectrum. Finally, we illustrate the connection between flat adjacent minima in the energy landscape and resonant phonon scattering through detailed analyses of the energy landscape of the defective structures. arXiv:1905.11056v1 [cond-mat.mtrl-sci] 27 May 2019 * ashis.kundu@tuwien.ac.at 1 S. M. Sze and K. K. Ng, Physics of semiconductor devices, John wiley & sons, 2006.

Combined treatment of phonon scattering by electrons and point defects explains the thermal conductivity reduction in highly-doped Si

“…Neither EPS nor PDPS can be captured by conventional parameterized models. Together with our previous works on doping diamond, SiC, GaN and GaAs, 34,[36][37][38] we show that, at temperatures above 300 K, PDPS is the most dominant scattering mechanism in highly B-and P-doped Si and cannot be neglected.…”

Identifying the ground state structures of point defects in solids

“…The dimer (DX-CCB) configurations are found to be more favourable than the broken bond (DX-BB) one, with energies of 0.30 eV (DX-CCB-α, DX-CCB-β) and 0.44 eV (DX-BB) relative to the ground state T d structure. Again, these results agree with previous local DFT (LDA) calculations, which found relative energies of 0.5 eV for DX-CCB (α & β) and 0.6 eV for DX-BB, relative to T d [114,115] . We note that our method did not locate the DX-CCB-β arrangement, likely due to a soft PES (with an energy barrier of only 25 meV between alpha and beta, SI Section VIII), the close similarity of structure and energies for DX-CCB-α/β, and the bias toward ground state configurations.…”

“…For Si, Sn and Te impurities, our method successfully identifies all low-energy metastable structures reported by previous studies, [108][109][110][111][112][113][114] while for S, it identifies two of the three structures previously found. [114,115] For instance, in the case of Si, we correctly identify the broken bond configuration (DX-BB) [108][109][110][111][112][113] , which entails a C 3v Jahn-Teller distortion with the dopant displacing along the [111] direction thereby breaking a Si-As bond (Fig. 7 (b)).…”

Efficient construction of linear models in materials modeling and applications to force constant expansions

“…The second-order FCs of systems with many atoms and/or low symmetry can be tedious to obtain by the direct approach. This applies in particular to the FCs of defect configurations, which are needed for example for computing the vibrational contribution to the free energy of defect formation 16 , analyzing the impact of defects on the thermal conductivity 18,38,39 or predicting the vibrational broadening of optical spectra 40,41 . In this section, we therefore analyze the extraction of second-order FCs for the vacancy in body-centered cubic (BCC) Ta as a prototypical case, using both the direct approach as implemented in PHONOPY 25 and the regression approach as implemented in HIPHIVE 15 .…”